1. Field of the Invention
The present invention relates to a water leakage monitoring apparatus, and more particularly to a water leakage monitoring apparatus which converts an acoustic vibration transmitted to a water pipe into an electric signal and presents data for making judgment whether water leakage is being caused or not on the basis of the electric signal.
2. Related Art
Social Background
Clean water to be used as drinking water or the like is distributed to every house through a feed water pipe branched from a distributing pipe. The distributing/feed water pipes (water pipe) have significant deterioration, and water leakage associated therewith is becoming a serious social problem. It has been said that current water leakage amounts reach more than or equal to 10% of the amount of water distributed as clean water. In every summer, a water shortage is caused around metropolitan areas. For compensating for the amount of water lost by water leakage, new service water resources have to be developed, incurring huge costs and significantly influencing the natural environment of the water source.
Accordingly, it has been required to quickly repair leaking portions of the water pipe to eliminate the loss of precious water resources. For this purpose, it is important to monitor the condition of the water pipe sequentially over a wide area to quickly detect water leakage.
Conventional Water Leakage Monitoring and Detecting Technology
Conventionally, water leakage in the water pipe has been detected by a man directly listening to an acoustic vibration transmitted to the water pipe. Water leakage inspection is performed at a time, such as midnight, when there is less traffic and use, and the amount of water becomes small, so as to avoid confusing acoustic vibration due to noise and normal water flow. Then, the water pipe, buried underground, is traced according to an installation map to make a judgment whether water leakage is present or not by listening by means of a stethoscope fitted on the ground or directly on the surface of the water pipe by a professional engineer to an acoustic vibration transmitted to the water pipe. However, in this method, the working hours are limited and the range of the water pipe to be inspected is quite narrow. Therefore, a huge amount of time is taken for identifying the water leaking portion from the wide inspection range. This makes it impossible to catch up on the certainly progressing deterioration of the water pipe. On the other hand, it is possible that water leakage cannot be detected certainly with the skill of the engineer performing the inspection.
Therefore, Japanese Unexamined Patent Publication No. Heisei 5-296824 (first prior art), Japanese Unexamined Utility Model Publication No. Heisei 6-12564 (second prior art), Japanese Unexamined Patent Publication No. Heisei 6-146346 (third prior art) and so on disclose technologies for water leakage monitoring apparatus which can detect water leakage automatically.
The first prior art converts a vibration transmitted to a pipe line, such as the water pipe, into an electrical signal and preliminarily stores a pattern of the electrical signal by adding an allowable range to an electrical signal corresponding to a vibration in the condition where a fluid is not flowing through the pipe line, as a noise component. Then, the electrical signal pattern while the fluid flows through the pipe line is compared with the noise component to make a judgment that water leakage is occurring when an electrical signal pattern different from normal fluid flow condition is detected.
On the other hand, the second prior art compares a water amount flowing in the water pipe indicated by a water meter interposed in the feed water pipe of each house with a preliminarily set water leakage amount to make judgment that water leakage is occurring when the water amount indicated by the water meter exceeds a set amount of the water leakage amount. Also, the third prior art monitors the water consumption amount output from the water meter and the vibration caused due to water flow and transmitted to the water pipe so as to make a judgment that water leakage is occurring when the vibration of the water pipe is detected while the meter does not show a consumption amount, i.e. water service is not in use.
The foregoing first prior art is basically directed to a water leakage monitoring apparatus in the water pipe for cooling a plant, and requires preliminary storage of the signal pattern of the environmental noise under the condition where water is not flowing. Therefore, it is difficult to apply this technology for an already-installed water pipe. On the other hand, a complicated digital data process, such as signal pattern recognition and so forth, is required and makes the apparatus per se expensive. Huge costs are inherently incurred if a large number of these apparatuses are installed for identifying the portion causing water leakage from the water pipe installation range.
The second prior art is water leakage monitoring technology for the case of an absence for a long period of time, such as with a cottage, and is premised on no water service being used while absent. Then, the water leakage of the water pipe on the inside of the building can be detected from the water meter. Accordingly, it is not applicable for that detection of water leakage in a general water pipe, to which the present invention directed.
The third prior art is premised on no environmental vibration due to ambient noise or environmental vibration due to traffic occurring when the water meter does not indicate water flow. Conversely, it is possible that the water service is used even in at midnight, when environmental vibrations are small. Therefore, the probability of detection of the water leakage is low, causing difficulties in quickly taking a measurement.
Here, considering the conventional water leakage detection method, it should be appreciated that the prior art judges that water leakage is occurring on the basis of obtaining certain information due to water leakage. However, in the current social environment, the water service is used day and night, and it is not likely that noise and vibration due to traffic or other reasons is interrupted for a long period. Therefore, it is difficult for the conventional water leakage detection technology to achieve leakage detection over a wide area, quickly and at low cost.
Therefore, the present invention has been worked out focusing on the fact that water leakage is continuous at a constant water flow rate without interruption, and normal water flow in use of city water is intermittent/irregular. Then, if the water pipe is in normal condition, vibration to be transmitted to the water pipe is intermittent/irregular. Therefore, an inference is made that the possibility that water leakage is occurring is quite low if no vibrating condition is detected, even for a short period in the order of several seconds. The cogency of this approach has been confirmed with a large number of experiments. As a result, the following invention has been made.
According to a first aspect of the invention, a water leakage monitoring apparatus comprises a vibration/electric converter for converting an acoustic vibration transmitted to a water pipe into an electrical signal. A signal discriminator processes an output signal of the vibration/electric converter to detect a signal of a predetermined band being held below a predetermined level continuously beyond a continuing condition so as to generate a sound interruption detection signal. A counter counts the number of occurrences of the sound interruption detection signal.
In a second aspect of the invention, the water leakage monitoring apparatus comprises a display for outputting a display of a count value of the counter. Accordingly to a third aspect of the invention, the water leakage monitoring apparatus comprises signal output for outputting the count number of the counter in the form of a data signal.
According to a fourth aspect of the invention, the water leakage monitoring apparatus comprises a manual reset for resetting the counter in response to a manual switch operation. In a fifth aspect of the invention, the water leakage monitoring apparatus comprises a timer circuit measuring time, and an automatic reset for storing the count value of the counter in a predetermined memory area in predetermined monitoring cycles and resetting the counter.
In a sixth aspect of the invention, the water leakage monitoring apparatus comprises a timer circuit for measuring time, water leakage judgment means for making a judgment as to whether water leakage is caused or not on the basis of times of occurrence of the sound interruption detection signal in predetermined monitoring cycles, a judgment result storage for storing the result of judgment by the judgment means for the predetermined cycles in a predetermined memory area, and a judgment result output for outputting the judgment result stored in the storage in display output or in the form of a data signal.
In a seventh aspect of the invention, the water leakage monitoring apparatus comprises a timer circuit for measuring time, water leakage judgment means for making a judgment that water leakage is not caused when the number of occurrences of the sound interruption detection signal is more than or equal to a predetermined number of times and making a judgment that water leakage is caused when the number of occurrences of the sound interruption detection signal is less than the predetermined number of times, a judgment result storage for storing the result of the judgment by the judgment means for predetermined cycles in a predetermined memory area, and a judgment result output device for outputting the judgment result stored in the storage in a display output or in the form of a data signal.
In an eighth aspect of the invention, the water leakage monitoring apparatus comprises a timer circuit operated constantly for measuring time, and an intermittent operation controller operated constantly together with the timer circuit for enabling other circuits by intermittently supplying operational power for other circuits on the basis of a predetermined time schedule.
In a ninth aspect of the invention, the water leakage monitoring apparatus comprises a controller for interrupting the operation of the monitoring cycle during detection of the sound interruption detection signal in certain monitoring cycles for predetermined times to halt the cycle.